Navigation instrument



, NAVIGATION INSTRUMENT Filedl March 51, 1958 2 Sheets-Sheet 1 52 Na7/$0 E? ff? i7 .52 55 625% W MT Z @Hman/m Dec. 3, 1940.

H. W. SLAUSON NAVIGATION INSTRUMENT Filed March 31, 1938 2 Sheets-Sheet 2 lll 2.

Patented Dec. 3, 1940 UNITED STATES PATENT OFFICE i Harold W. Slauson, Scarsdale, N. Y.

Application March 31, 1938, Serial No. 199,223

1 Claim.

This invention relates tov navigation instruments and particularly toplotting and charting devices for laying and determining courses from hydrographie or other charts and maps.

It is the general object of the present invention to provide an improved device for the above mentioned purposes which does not require reference to the compass rose on the chart so that large charts can be used in a folded condition for convenience in crowded quarters.

An important object of the invention consists in the provision of a device including a small base having means for attaching a chart securely thereto and carrying an instrument including a scaled `rule which may be moved anywhere on the face of the chart Vwhile always remaining parallelto its initially set position, and which is adjustable in respect to a protractor-like scale for determining course angles in respect to thel true or the magnetic meridian.

Another important object of the invention is to provide an instrument and mounting board containing clamps for charts or the like, the whole of which can be folded into extremely small compass, the clamps holding the instrument on the base which forms the base of a carrying case or cover. l

An important feature of the invention resides in the provision of mechanism for carrying the protractor and scale which imparts a parallel motion thereto and which itself is adapted to be clamped to the edge of a drawing board, chart table or the like, together with a small base 0r board having clamps thereon forsecuring a chart in position in the proper relationship to the instrument and which has a special point of application for theinstrument whereby the whole can be folded into the small compass of the board, retained by the chart clamps and readily housed in a convenient carrying case.

Other and further features and objects of the invention will be more apparent to those skilled v in the art upon a consideration of the accompanying drawings and following specification, wherein is disclosed a single exemplary embodiment thereof with the understanding that such changes may be made therein as fall within the scope of the appended claim without departing from the spirit of the invention. In said drawings:

Figure 1 is a plan view of the apparatus of the present invention shown with a vchart mounted thereon for the purpose of determining the course of a vessel in the waters depicted on the chart; l i

Figure 5 is a View similar to Figure 4 taken 10A at right angles thereto on line 5--5 of Figure a showing the instrument clamp in elevation;

Figure 6 is a section on line 6 6 of Figure 2 showing one of the chart clamps in elevation; and

Figure 7 is a perspective View of the cruciforrn 15 connector for the sets of parallel arms.

The present invention while heretofore referred to as a device for use in navigatingv ships, boats or the like, is nevertheless equally as applicable to the similar practices in aviation. 20' Most airplanes as well as the majority of small boats sulTer from a lack of space for using charts. The time-honored method of determining the-` angle of or laying out a course in respect to the true or magnetic meridian has been to place a 25 parallel ruler or a protractor combination on the course and move the same `across the chart to the compass rose printed in one corner thereof and on this rose read oif the angle.

The customary form of parallel ruler comv30 prising a pair of blade-like members connected by parallelpivoted arms is operated in an awkward manner by holding one blade on the chart and stepping `the other, then holding the second and bringing up the rst, and errors existing in 315V the instrument are thus cumulative. In addition there is always the possibility of slippage which if detected requires the procedure to be repeated and if undetected, results in serious error which may be disastrous. The rolling form .m of parallel ruler and the protractor combination are likewise subject to the difculties of slippage and require an extremely smooth flat surface for their operation. Otherforms of apparatus which are not so well known or so universally used are 45 subject to the same diniculties, the principal one of which, except for the erroneous operation referred to above, is the requisite for a space suniciently large to open out the chart so that the course can be referred to the compass rose. Most 50' charts are of large size, approximately 30" by 40" and sufficient space is not always available for this purpose excepton boatsand planes provided with a separate chart room or table. Moreover the use of a parallel ruler or the ordinary promit tractor requires two hands so that the skipper cannot handle the boat while charting his course even if he has sufficient space to lay out a chart near the wheel or tiller.

In accordance with the present invention the charts can be used folded, showing on the exposed face only that portion of the same over which the course is to be determined. This results from features of the device making it unnecessary to refer all courses back to the compass rose. The apparatus can be used with one hand and requires only a small space.

Where magnetic courses are used the compass variation must be known, and this is marked on the rose or is. available from nauticall almanacs.

` It need be made use of but once in setting the chart as will be subsequently described. Likewise compass deviation can be compensated for when Y the amount is known.

Referring now to the drawings, and particularly to Figures 1 and 2, there is shown a small substantially rectangular baseboard i0 that is longer than wide and that is Vnot nearly so large as even the folded size of a chart. Its size is merely sufficient to receive the instrument completely folded thereon as shown in Figure 2. It may be made of suitable ply board, plastic composition, or the like, is preferably substantially rectangular and carries attached along its upper edge a pair of spring clips il of the general configuration shown in Figure 6 each mounted on the sh-ank of a screw i2 extending through the base, resting on a nut i3 thereon and adapted to be clamped in position by a thumb nut i4. The

bowing of each clamp is such that when the `substantially1 universal parallelv motion mechaism including the head i8 carried bythe parallel arms i9 attached thereto at pivot points Eil; `the cruciform member 2i carrying the pivots 22 for the opposite ends of the` arms l spaced apart the same distance as the ypivots 20. On an axis at right angles to that passing through the pivots `for one end of a pair of parallel arms 25, extend- 22 and below the same are mounted the pivots 254 ing to the pivots 26 with the same spacing as the pivots Elli onv the clamp member 2l, best seen in Figure as comprising a U-shaped device having the top 253, the bottom arm 29 and the connecting member dii. The bottom arm is received against the underside of the baseboard I0, the member 30 against its edge, while the upper arm 28 extends over the upper surface of the base and carries a pair of clamp screws 3l adapted to be manipulated by the knurled heads 32 .to secure the clamp firmly to the base in any desired position along its edges.

The parallel motion mechanism just described permits the head I8 to be moved over a definite area of chart always parallel to its initial position, thereby oiiering means for determining the angularity of a course on the chart in respect to the `true meridian as indicated by any of the longitude lines 3d on the chart or for that matter to the latitude lines or parallels 35.

To permitfthis the head i8. has pivotally se- ,cured beneath it the, graduated disc or protractor 36that simulates the `compass roseon the chart, exceptthat the graduations on this disc are prefvides a convenient operating handle for moving the instrument over the surface of the chart and at the same time permits locking of the disc at the desired angle in respect to the head.

The disc carries preferably integral therewith the ruler or scale 50, the upper marking edge 5| of whichv is parallel to the Zero-180 diameter of the graduated disc.

This edge, as well as the opposite edge 52, may conveniently be graduated to any suitable scale to replace the usual dividers resorted to for transferring distances to a scale. It may have the usual inch marks with suitable t intermediate graduations, or it may have engraved thereon a scale of miles either nautical or statute, preferably in one or more of the ratios used onmost chart-s, for instance 1 to 80,000.

The construction of the apparatus is such that the scale 59 has its upper edge preferably tangential to the periphery of the attached protractor portion. Because of the vertical offset 53 in the head i8, the arms i9 may move above the scale and it is permittedto rotate through a full 360 without interference with any of the parts of the mechanism carrying the same.

Because of the mounting of the protractorruler it may be used in a reversed position.' The under face cf the disc may be graduated in compass points to satisfy those, desiring to work with them and other scales maybe applied to the edges of the ruler if desired.

The arms carrying the pivots 22,011 the cruciform member 2i are offset upwardly as shown in Figure 7 to permit the vparallel links i9 to move Vabove the parallel links 25 when necessary so that there is no interference between the same. This arrangement of parts permits the apparatus to be folded into a compact assembly as Vshown in Figure 2 with the scale substantially parallel to the arms i9 and with them 'overlapping the arms 25. In order that the clamp 2l may be attached to the baseboard Iii when the apparatus is folded for packing, one corner of thebaseboard is clipped at the angle shown at 55 which accommodates the clamp 2l when the apparatus is compacted.

The clipped portion 55 is longer than the length of the clamp 2l, as can be seen in Fig. 2, and is designed so that when in; the folded position shown in Fig. 2, the clamp 2l lies wholly within the rectangular contour lines of the base i. If the clamp were put on the'straight edge of the baseboard as shown in Figure 1, the apparatus could not be arranged within the compass of so small a base. With the arrangement shown in Figure 2 the chart clamps H can be secured over the scale 5d to hold the same in position and prevent the parts of the apparatus from moving on the base.

The edge of the baseopposite that onwhich the clamp 2T is applied for packing the instrument has extending therefrom several metal pins or dowels 58 which, as seen in Figure 3, are adapted to be'received longitudinally in holes in the side member 51 of a box of just sufficient size to slip around the edges of the base member. TheV sides 51 and 58 as well as end members 59 and 60 are secured about a bottom member 6I in any suitable manner, the depth of the box being just adequate to receive the apparatus when the base is set in as shown in Figure 3 to house the bottom of the clamp within the plane of the bottom edgesY ment and since the base forms the coverof they box there are but two parts when it is removed therefrom.` The base takes the place of a chart table or board in spite of its small size so that the apparatus can be used in various places about asmall boat or plane `and actuated with one hand to rapidly `accomplish what required a large table or chart board, two hands, considerable time and some degree of skill with the old equipment.

To use the apparatus the base is removed from the box, the clamp removed from and applied as inFigure 1, and a chart, folded to suitable size to expose 'only the portion required for 'the course to be plotted or whose angle is to be determined,

is suitably arranged beneath the clamps H which are tightened down just sufficiently to hold the chart in position but tov permit it toy be moved. The protractor is then set in respect to the N index to show the exact degree of compass variation and if desired the deviation, thetwo being added algebraically. With this setting clamped by means of the knurled nut 45 Vthe scale is brought adjacent one of the lines of longitude 34and the chart twisted beneath its clamps until this line is parallel to the edge of the scale. The clamps I I are then tightened down to insure against slippage of the chart in respect to the base.

After this initial setting any course line may be plotted, or the angle of one already plotted deterf 3 mined by merely laying either edge of the'scale llalong the line vand reading the protractor. The reading of the protractor will then give the compass course to sail if the compass deviation hasA been added to the variation determined from the` compass rose or the nautical almanac.

If it is desired to sail true course rather-,thank magnetic the initial positioning ofthe chart is effected with the protractor set to Zero.

It will be seen that-with the above instrument the direction of a course can be read off instantly at the protractor without any reference whatsoever to the compass rose which may be onthe far corner of` the chart fromthe course being plotted. ,Moreoven the arrangement for initially setting the chart with respect to the base elimi- `hates the need for making corrections for variationand deviation and thus the possibility of several serious errors. c,

Having thus described the invention, what is claimed as new and desiredto `be secured by,

Letters Patent is:

A navigation instrument including in combination, a substantially rectangular ,base longer than wide for supporting a nautical chart, chart holding clamps extending from the upper edge thereof, a ruler terminating in an yenlargement bearing a compass rose, a squared plate marked with the cardinal points `of the compass, clamping means for adjustably securing the compass rose beneath the squared plate, a clamping member substantially U-shaped in cross-section adapted toreceive adjustably the edge of thebase within the U, mechanism of parallel link type for supporting the plate and its ruler from the U-shaped clamping member;` said base being smaller than a standard nautical chart and at its lower edge having a corner cut yaway at an angle for a distance longer than the clamping member for receiving said clampingmember in `a position so that the `clamping member is wholly inset within the rectangular contour lines of the base whereby v when the clamping member is so disposed, its link mechanism and ruler are foldable `wholly within the contour outline ofthe base and clampable in such position` by said chart holding clamps.

HAROLD W. SIiAUSON. 

